Many of us pay a huge premium at the grocery store for items that are labeled as "organic" — or feel guilty if we don't. The coveted "organic" label is supposed to mean something is all-natural, and therefore better for you. But it's not true.

A recent study suggests the $27 billion organic food industry is based on a myth.

Research from Stanford University suggests that organic foods do not offer more nutrients and vitamins than regular foods — a conclusion that could have a profound impact on an industry that has grown to $27 billion per year in the United States. But the researchers also discovered, however, that organic foods do contain lower levels of pesticides in fruits and vegetables, and antibiotic-resistant bacteria in meat — so you might not want to make that switch back to conventional foods just quite yet.

The researchers, Dena Bravata, Crystal Smith-Spangler, and others, reached this conclusion by reviewing 240 studies — 17 of which were clinical trials of people on both organic and conventional diets, and 223 studies that looked into nutrient and contaminant levels in foods.

It's important to note that, for the clinical trials, the researchers did not look into any long-term studies of health outcomes of people eating organic versus conventionally produced foods. At most, the duration of the trials ranged from two days to two years. In addition, the researchers admitted that the studies were heterogeneous (meaning that they employed various methodologies and scope), and limited in number.

Now all that said, analysis of all this data showed no significant differences between the health of organic food eaters compared to conventional food eaters, particularly when it came to such things as allergies (like eczema) or Campylobacter bacterial infections.

Moreover, they found little significant difference in the vitamin content of organic products, with only one nutrient, phosphorus, appearing in organic foods at significantly higher rates (which isn't really an issue considering how few people suffer from phosphorus deficiencies).

In addition, the researchers found no difference in protein or fat content between organic and conventional milk — though they did find evidence that organic milk may contain considerably higher levels of omega-3 fatty acids (which is quite significant from a health perspective).

But what the researchers did discover was that lower pesticide levels could be detected among children who ate organic foods compared to those on conventional diets. The researchers found that organic produce is 30% less likely to be contaminated with pesticides than conventional fruits and vegetables — but they cautioned that the differences in biomarkers and nutrient levels in serum, urine, breast milk, and semen in adults were not "clinically meaningful."

They conclude the study by noting that the published literature lacks the evidence to suggest that organic foods are significantly more nutritious than conventional foods.